The present invention relates generally to sensor systems, and more particularly to differential motion sensors such as shear or tensile-responsive electromechanical fuses.
Differential motion sensors detect transverse motion of one piece or section relative to another, adjacent piece or section. Differential motion sensors are used in a variety of aerospace applications, including in failure detection for aircraft wing vanes. Differential motion sensors are typically mounted across at least two separately moveable components to sense transverse motion therebetween.
Some differential motion sensors include electromechanical fuses that bridge an electrical gap. These fuses break in tension when sufficient shear occurs, opening an electrical circuit. Differential motion sensors of this type are ordinarily mounted on one component, and have lever arms that extend to engage a pin or stud on a second, adjacent component. Shear deflection (i.e. transverse motion) of one component relative to the other applies tensile load to the lever arm, resulting in increased tensile load on the fuse. Under high tensile load, the fuse fractures mechanically, creating an electrical gap that can be detected by a connected controller. Fuses are relatively expensive and complex to manufacture, and must be replaced in order to reset this type of sensor. In addition, these kinds of electromechanical fuses break at a fixed tensile load threshold that cannot be adjusted without redesign.